Method for the fractional crystallization of cottonseed oil



Oct. 27, 1959 J. RUBIN ET AL METHOD FOR THE FRACTIONAL CRYSTALLIZATION OF COTTONSEED OIL Filed Oct. ll, 1955 WMHZEWQQEMF QZEUME I91 KUJOOUMEQ INVENTORS BY WzZ/zelm 6. [Ye/rims 6 ATTORNEYS 2,910,363 Patented Oct. 27, .1

METHOD FOR THE FRACTIONAL CRYSTALLIZA- TION F CO'ITONSEED on.

Leon J. Rubin, Downsview, Ontario, and Barton F. Teasdale and Wilhelm G. Mertens, Toronto, Ontario, Canada, assignors to Canada Packers, Limited, Toronto, Ontario, Canada Application October 1'1, 1955, Serial No. 539,820 Claims. (Cl. 99- 118) This invention relates to the fractional crystallization of oils, and more particularly to a solvent method for the fractional crystallization of oils wherein a smaller quantity of solvent is utilized to facilitate removal of higher-melting triglycerides and produce a winterized product than heretofore believed practicable.

While not limited thereto, the invention is especially adapted to the treatment of certain naturally-occurring vegetable oils, such as cottonseed oil, to provide a winterized product suitable for use as a salad oil, and, for convenience, will be described hereinafter with relation to treatment of such oils. However, it is contemplated that the invention may be utilized in the treatment of oils from other sources, either naturally-occurring as in the case of animal and marine oils, or synthetically produced as in the case of oils produced by hydrogenation and/ or molecular rearrangement.

The Winterization of cottonseed oil by removing some of the higher-melting triglycerides to provide a fraction suitable for use as a salad oil has been practiced for many years. The original method for Winterization consisted of storing the oil in outside tanks during the winter, whereupon it became chilled to such an extent that crystals of the higher-melting triglycerides would settle out. Winterization by this method is now carried out under more closely controlled conditions in refrigerated rooms where the oil first crystallizes in large tanks and is then filtered through the plate-and-frame filter presses. This method, however, is very slow and requires large and expensive processing equipment. It is diflicult to obtain good-sized, easily-filtered crystals from the viscous, cold oil, and a very slow rate of cooling is necessary. The oil is usually cooled to a temperature of about 45 to 48 F. and must be held at this temperaturefor at least about ten or twelve hours prior to filtering. The total time necessary for the process may be between about 30 and 50 hours, and even under the most favorable circumstances the final separation of solids and liquids is slow and incomplete.

Improvements in the Winterization of oils have been made by the use of fractional crystallization from solvents. By this method and equilibrium between the solid and liquid phases is established much more rapidly; large, easily-separable crystals are produced even at relatively high cooling rates; and the viscosity of the liquid phase is reduced, so that separation of the crystals by filtration or other means is more rapid. A common characteristic of these solvent-crystallization methods is the use of relatively high amounts of solvent, i.e. sufiicient solvent is utilized to completely dissolve the bulk of the oil therein. Both polar and nonpolar solvents and mixtures thereof have been proposed for effecting such solvent crystallization. However, in all of these methods a relatively high solvent-oil ratio is employed, the average being about three parts of solvent to one part of oil. This high amount of solvent is disadvantageous from the viewpoint of economy because both the size of the processing equipment and the solvent loss by evaporation for production of a given quantity of product are proportional to the quantity of solvent employed. The higher the quantity of solvent, the greater must be the capacity of the chilling units, holding units, and solvent-recovery units. The quantity of solvent lost by evaporation, which may average about 4%, becomes an important economic factor where high quantities of solvent are employed. Nevertheless, it has always been thought necessary to use relatively large quantities of solvent to provide a readily separable crystallized fraction.

In general, it has also been considered necessary to use relatively low temperatures to obtain a sutficient speed of crystallization, temperatures from 3 to 60 C. being commonly used, thereby necessitating an expensive refrigeration system where the process is operated on a commercial scale. The solvent crystallization processes do, however, have the advantages of a relatively short chilling period and short hold-up time. The total time for chilling and crystallization is reduced to less than about four hours in some cases. Also, the salad oil resulting from these processes is of a higher quality than that obtained by the conventional Winterization method utilizing nosolvent.

A salad oil is defined as an oil which will remain liquid and will not cloud up or form crystals at refrigerator temperatures F.), and which will produce a mayonnaise emulsion whichis stable at those temperatures. The American Oil Chemists Society (A.O.C.S.) method for evaluation of salad oils is the cold test by which the tendency of the oil to form crystals at 32 F. is measured. The oil sample, in a sealed 4-oz. bottle, is put into a bath of melting ice (32 F.) and the time is measured until the first crystals occur in the oil. A cold test, by this method, of 5% hours is considered to be suificient for a salad oil, but

, higher cold tests are desirable, and will mean a quality treated whereby rapid chilling,

improvement. With conventional methods for winterizing salad oils, it is difiicult to obtain cold tests as high as 20 hours, and rarely can higher cold tests be obtained.

An object of the present invention is to provide a relatively simple and economical process for treating oils which require Winterization so that they will meet the aforestated requirements for salad oils.

Another object of the invention is to provide a process for Winterizing oils which readily lends itself to continuous operation.

Another object of the invention is to provide an improved method for Winterization of oils which possesses substantially all of the advantages of the solvent-crystaL lization processes as heretofore practiced, but in which the solvent loss is materially reduced and in which excessively low temperatures are unnecessary.

Another object of the invention is to provide a process for the fractional crystallization of oils wherein a relatively small quantity of a selected solvent is employed to facilitate crystallization of the higher-melting triglycerides.

Another object of the invention is to provide a process for the fractional crystallization of oils in which a small quantity of a selected solvent is added to the oil to be and relatively short holding periods for effecting crystallization may be utilized.

A further object of the invention is to provide an improved method for producing a salad oil having a high cold test and a good yield from vegetable oils, by virtue of using a relatively small quantity of a selected solvent and critical temperature conditions during the fractional crystallization of said oils.

A further object of the invention is vto provide a soltonseed oil wherein low quantities of a selected solvent moderate temperatures,

are utilized and wherein it is unnecessary to chill to extremely low temperatures to provide a readily separable crystalline fraction.

Another object of the invention is to provide a solventcrystallization method for the fractionation of oils utilizing asmall quantity of solvent, rapid chilling, and a shortover-all processing time, and wherein good yields of a high-quality winterized oil are obtained.

It has been discovered that these and other objects and advantages hereinafter apparent can be accomplished by adding to the oil to be processed a very small quantity of a selected solvent which is completely miscible with the oil, and which, in effect, is dissolved within the relatively large volume of the oil, and by then chilling. the oil containing the dissolved solvent to a critical temperature which is maintained for a short hold-up time to permit crystallization of the desired fraction to be completed. By proper correlation of solvent selection, solvent quantity, and temperature conditions, a readily filterable .mass' is produced, providing a high quality product in high yield.

The invention ingeneral, comprises admixing less than 20% by weight of the selected solvent with the oil,

rapidly chilling the resultant mixture to a temperature within the range of about F. to about 39 F., maintaining the temperature of the mixture within this range for about three to four hours to crystallize the highermelting triglycerides, separating the crystallized triglycerides from the product oil, and removing the solvent from the resulting winterized oil. The resulting winterized oil, which, in the case of cottonseed oil is suitable for salad oil, has a cold test of from 15 to 20 hours. Longer holding times will provide longer cold tests, and. cold tests of up to 60 hours may be obtained with holding times offrom 6 to 8 hours.

.As solvents for-the present process, the low-molecular weight ketones, acetates, ethers, and aliphatic nitrogen compounds in general may be utilized. In at least one of these solvent groups there is a tendency for increasing rate of crystallization as one goes from the lowmolecular-weight members to the higher-molecularweight members. For example, satisfactory rates of crystallization are obtained with acetone, methyl ethyl ketone and methyl isobutyl ketone, although the methyl isobutyl ketone provides a mixture which is slightly stiff aftera 4 hour hold-up time, rendering it slightly more dlfi'lCllll'. to filter. Ethyl acetate and isopropyl acetate provide generally good results. Butyl acetate results in a mixture having a rather high viscosity because of fast crystallization which renders the mixture more difiicult to. filter. Ethyl ether provides good results although the low boiling point of this solvent is disadvantageous for practical applications. It has also been found that dimethyl-formamide, a disubstituted aliphatic amide, may be utilized with good results although this solvent provides better results at around 20% by weight than with lower quantities.

The alcohols, hydrocarbons including hexane and benzene, chlorinated hydrocarbons, petroleum ether, toluene, and tetrahydrofuran were found to be unsuitable when used in quantities within the preferred range, either because of insolubility in the oil, undesirably slow crystallization, or,- in some instances, undesirably fast crystallizati on resulting in stiff, gelatinous masses which could not be separated.

The preferred quantity of solvent is less than about- 20% by weight based on the weight of the oil, with 10% being satisfactory for acetone and all of the other preferred solvents except dimethyl formamide, which provides better results at the upper portion of the range. Contrary to expectation, good-sized, well-defined, easilyfilterable crystals are produced by using such'amount of solvent, provided other critical conditions of the process are observedi For operation with low quantities of solvent in accordance with the present invention, the temperature to which the mixture is chilled and maintained throughout the holding period is a very important and critical feature, as the crystallization rate depends upon the relation of temperature to the amount of solvent. In general, the lowering of the holding temperature will increase the crystallization rate and shorten the process.

However, too low temperatures will result in a fastsetting, stiff, gelatinous mass which can be'separated only by the addition of more solvent. As the operating temperature is lowered below the preferred temperature, higher amounts of solvent are required to obtain satisfactory separation. In order to realize the advantages of the present invention, the temperature should be lowered only to that extent which will provide an easilyseparable product with quantities of solvent less than 20% and in no instance need be lower than about 25 F. It is preferred to utilize a precooling step for the oil to reduce its temperature to within a range of from about 40 F. to 50 F. before adding the solvent. However, this is primarily a matter of convenience, as the preferred solvents will dissolve very readily in oil having. somewhat lower temperatures as well as at higher tem peratures. However, at higher temperatures there may be the disadvantage of solvent evaporation. The temperature of the oil to which the solvent is added may without disadvantage vary between 40 F. and 60 F.

Regardless of whether precooling is utilized, chilling to the lower temperature range is preferably accomplished by rapid chilling methods, and it has been found that use of small, externally-cooled cylinders provided with scraping means, such as a Votator A Unit described by Bailey in Industrial Oil and Fat Products, Intersciences Publishers, Inc., New York, N.Y., 1945, pp. 702 to 707, is suitable for this purpose. The outlettemperature of the oil-solvent mixture from the Votator A Unit or other rapid-chilling unit is preferably about 32 F. with 10% solvent in the mixture and may vary between 31 F. and 34 F. This temperature is desirably the same temperature as that utilized in the hold-up period, so that no more cooling need be applied-in the storage room, except that required to maintain the temperature at a substantially constant value. Thus, a temperature within the range of from 31 F. to 34 F. may be maintained during the holding and crystallization period when utilizing 10% solvent. If the temperature drops substantially below this range, the oil-solvent mixture crystallizes very fast and sets up to a stiff, gelatinous mass. If the temperature rises materially above 34 F. the crystallization rate is too slow and the sample stays too liquid, thereby requiring longer hold-up times to'provide the same amount of crystallization. For a hold-up time of from 2 to 4 hours, it is therefore desirable that the temperature remain below 34 F., although operating temperatures of up to 38 to 39 F. would be possible with a considerably longer holding period. Whenthe temperatures below about 31 F. are utilized, more solvent is required to prevent the sample from turning stifr". By using about 15% by weight of solvent, satisfactory crystallization and slightly shorter hold-up times may be utilized witha temperature as low as about 28 F. Temperatures of as low as 25 F. require approximately 20% by weight of solvent for satisfactory operation. Accordingly, 25 F. is regarded as the lowest practical temperature for the present process. It will be understood that a certain amount of heat of crystallization is released during the hold-up period, and therefore the process requires some cooling duringthis period to maintain the temperature within the desired range.

It will bev observed from the foregoing discussion that the solvent concentration is closely related to the tern-- perature of the process, with solvent concentrations of;

% being preferred for temperatures of around 32 F. with all of the selected solvents except dimethyl formamide. While the use of by weight of solvent in admixture with the oil gives good results at slightly lower hold-up temperatures, i.e. 28 F., the gain in over-all time due-to faster crystallization at lower temperatures is not significant. The use of a solvent concentration for all of the solvents, except dimethylformamide, at 32 F., in general, provides a crystallization rate which is rather slow and therefore requires unnecessarily long hold-up times. Accordingly, 20% by Weight of solvent is considered the maximum practical limit without employing undesirably low temperatures and long hold-up periods. It will be understood that an increase in hold-up time at all temperatures in the preferred range will result in slightly lower salad oil yields, but that the oil will be of a higher quality and have a better cold test by so operating. By varying the hold-up time, an adjustment of final salad oil properties according to the desired specifications may be realized. By using 10% by weight of solvent at 32 F., and a hold-up time of 3 to 4 hours, with slight agitation of the mixture during such period, a salad oil is obtained which has a cold test of from 15 to 20 hours.

By increasing the hold-up time to about 6 hours under the same conditions, a cold test of 30 to 40 hours or more can be readily obtained.

Water, which may be absorbed from the ambient atmosphere or may be dissolved or suspended in the oil to be treated, may tend to build up in the solvent, and where a solvent in which water is highly soluble or is completely miscible, as acetone, is employed, it may be desirable to periodically separate the Water from the solvent before the latter is reused. However, it has been found that a small quantity of water in the solvents in the present process provides no significant difference in the Winterization behavior. Water-miscible solvents such as acetone may be satisfactorily utilized with a water content of at least 4%, and solvents in which Water is less soluble may be used when containing any amount of water up to saturation. Thus, in general, the presence of a small amount of suspended water in the oil to be treated provides no problem, regardless of the degree of water-solubility of the Water in the selected solvent, and no dewatering is necessary. However, where larger quantities of water are encountered, it is preferred to use a solvent in which water is soluble to only a limited degree, such as methyl-ethyl ketone, ethyl acetate, or isopropyl acetate. When these solvents become saturated, further moisture merely settles out of the oil-solvent solution. Thus, after the solvent has become water-saturated, the process may be run under very stable conditions without regard to the quantity of water in the oil or atmosphere. The crystallization rate is speeded up to some extent during the hold-up period if slight agitation is applied to the oil-solvent mixture. This agitation helps to contact all of the oil portions with the first crystal nuclei, giving uniform and fast crystallization. While initiation of the crystallization stage can be speeded up by the addition of seed material, such as cottonseed press cake, either before or after the addition of the solvent, it has been found that the subsequent rate of crystallization is speeded up too much by such procedure and the material turns undesirably stilf before giving the highermelting glycerides a chance to separate. Accordingly, no seeding is utilized in the preferred procedure.

Separation of the crystallized portion from the liquid product at the end of the hold-up time can be accomplished by conventional filter-press methods or by centrifuge. Continuous filters may be utilized or substantially continuous operation may be achieved by utilizing a pair of batch type filters with one on a filtering cycle while the other is being cleaned.

For further description of the invention, reference is made to the drawing which illustrates diagrammatically equipment for continuous operation of the process. A container 1 is provided for the oil to be processed, which may be a refined bleached cottonseed oil. This oil may flow by gravity through pipe 2 and control valve 3 to a precooling tank 4 provided with agitating vanes 5. The flow rate and cooling rate are preferably adjusted so that the oil issues from the tank 4 into outlet pipe 6 at about 50 F. A container 7 is also provided for the solvent, which, for example, may beacetone. The outlet pipe 8 from container 7 and oil pipe 6 from precooler 4 lead to a suitable proportioning pump 9, which may be adjusted to supply solvent to the oil in the proportion of 10% by weight. The oil-solvent streams are joined in a common pipe 10 which is of sufficient length to provide a residence time therein. of from at least one to three minutes to provide thorough. mixing and dissolution of the solvent in the oil. The oil-solvent mixture passes from pipe 10 into a chilling unit 11 of the Votator type, provided with scraping blades 12. The mixture is chilled in the unit 11 to a temperature of about 32 F. The flow rate through the chilling unit and the rate of heat exchange are preferably adjusted according to the hold-up facilities and the separating equipment for the crystallized oil.

The mixture from the chilling unit 11 is then run at a temperature of 32 F. through pipe 13 into a closed holdup tank 14 of sulficient length to provide a continuous hold-up system, where it may be maintained for about 3 to 4 hours to permit sufiicient crystallization. The tank 14 is provided with a series of baffies 15 to provide gentle agitation of the material as it continuously passes therethrough. A cooling jacket 16 is provided through which a coolant may be passed to extract heat of crystallization, such cooling being necessary to maintainsubstantially constant temperature. With 10% by weight of solvent, the mixture is maintained during this period at a tem perature of about 32 F. The partially-crystallized mixture from the hold-up tank 14 is then passed through pipe 17 and control valve 18 to a separating device shown as a centrifuge 19, where the crystallized fraction is sep arated from the liquid fraction. It will. be understood that filters of other types, such as a continuous rotary filter or a pair of plate and frame filters might be substituted for the centrifuge 19.

The liquid fraction, in which a portion of the solvent remains dissolved in the oil, is passed from the centrifuge 19 through pipe 20 by means of pump 21 to a still 22 for solvent recovery. Still 22 is provided with a steam coil or other heating means 23. The product oil is withdrawn from the still 22 through a pipe 24 and 'valve 25 to a container 26, after which it may be further treated by conventional means (not shown) for deodorization and removal of any small remaining quantities of solvent. The vaporized solvent is withdrawn through pipe 27, con densed in a condenser 28, of any conventional type, and pumped by pump 29 through pipe 30 back to the solvent container 7 for reuse.

The solid fraction from centrifuge 19 containing the remaining portion of the solvent may be melted and pumped through pipe 31 by pump 32 to a still 33 having a steam coil 34, wherein it is also stripped of solvent. The resulting oil is withdrawn through pipe 35 and valve 36, and may be used for any desired purpose. Vaporized solvent is withdrawn through pipe 37 and joins that in pipe 27 going to the condenser 28.

While a system for continuous operation has been de scribed, it will be understood that batch operation may be utilized if desired, with a large tank or series of tanks being used to provide the necessary hold-up space. In this instance, such tanks may be provided with means for effecting gentle agitation of the chilled mass during crystallization, and may further be provided with cooling coils for removing heat of crystallization.

ln order to maintain constant' temperature-conditions, the whole roomcontaining the precooling, chilling, holding, and separatingequipment may be refrigerated to about-32 F. This area is indicated by the dot-dash lines in the drawing. 7

Since the fat crystals are in a semi-solid state and can easily be der-nolished, deformed, or broken up,centrifugal pumps and gearpumps are generally unsuitable for movingthemass after crystallization has been initiated, and the mixture is preferably moved from the hold-up unit to the filter or centrifuge either by applying .air pressure direct-lytothe hold-up'tank or by utilizing the pressure of the-Votator or proportioning pump for pushing the material through-the whole system. Diaphragm pumps can also be utilized if desired.

Typical examples of operation of the process of the invention areas follows:

Example I ZOO-lbs. of refined, bleached cottonseed oil were precooled to 50 F. and mixed with by weight of acetone. The mixture was run continuously through a Votator A- Unit where it was rapidly chilled to 32 F., and thence-through an interconnecting pipe line directly into a cooler, where it was filled into 20 lb. pails. The flow rate was adjusted to the speed of filtration, and the mixture was given a hold-up'time of 2-3 /2 hours in the cooler at. 32 F.

An air-operated diaphragm pump was used to force the crystallized mass through a filter-press provided with duck filter cloth to filter the solids out of the mixture. The cold test of the salad oil (after solvent evaporation) was-z.

8 ethyl ketone. 7 The same test-conditions as in ExampleII were used. Results:

I.V. Cold Test The liquid portion from the centrifuge 112. 2 16% hrs. The solid portion out of the centrifuge; 86. 6 Control oil 107.5 Below 1 hour.

The yield ofsalad oil was about 80%;

Example IV Chilling time: I.V.' Cold test 3 hours 108. 6 1% hrs. 4 hours 112. 4 9 hrs.

113. 7 263 hrs. Control oil 107. 5 Below 1 hr.

Example V 100 g. refined, bleached cottonseed oil were mixed with 10%. by weight ofwater-saturated methyl ethylketone-(approximately 11.9% H O) inan Erlenmeyer Hold-up time I.V. Cold test flask. The same test conditions were. used as in Ex-.

ample 1V. Results: 106.8 Bclowlhr. 112.1 17 hours. 112.2 30 hours. 40 118-2 50+110urS- Chilling time I.V. Cold test 3houis- 108:9 3liours. The yield of salad oil after'ahold-up period of 3 /2 $832 at; fi fig$g hours was about75%. Control 0il- 107.5 Below1hr.-

Example II 800 g. of refined, bleached cottonseed oil were pre Example VI cooled to F. and mixed with 15% by we ght f 50 100 g. refined, bleached cottonseed oil werev mixed tone in a stoppered glass flask. The sample was cooled to 2830 F. in anice salt mixture and stored at this temperature without agitation for 3 /2 hours. The crystals were separated from the liquid by using the clarifying. bowl of a laboratory size Sharples super centrifuge, runwithv about 6500 g as centrifugal force. The sam ples were put on a hot plate, the solvent was evaporated under a stream of nitrogen and the samples were tested. Results:

The yield of salad oil based on the liquid portion from the centrifuge was about 80%.

Example 111 800 g1 of refined, bleached cottonseed oil were precooled to 50 F. and mixed with .15 by weight of methyl with 10% by weight of a solvent consisting of 96% acetone and 4% water. The sametest conditions were used as in Example IV. Results:

Chilling time I.V. Cold test 3 hours 109: 7 2% hours." 4 hours; 112.7 19 hours. 6 hours 113. 9 26 hours; Control oil 107. 5 Below 1 hr.

Example VII A further series oftests was conducted'with 10% solvents at 32 F. holding temperatures as in Examples IV through VIwitlr the following solvents':

The results of such tests are shown in the following table:

Holdup Solvent type tlme, hours 3hrs. 108.7 110.1 109.2 108.7 109.3 108.7 108.4 107.8 4hrs 112.5 112.8 114.3 1126 113.1 111.7 110.1 111.4 6hrs 114.0 114.3 114.1 114.6 113.4 114.1 113.11 114.1 Cold test,

hrs:

3hrs 2% 2% 2 1% 2 1% 1% 1% 4hrs 17 21 20 9 14 s 4 5 6hrs 3e 25 39 4s 4s 24% 41 25 Control oil I.V.: 107.5. Cold test: below 1 hour.

Example VIII Chilling time I.V. Cold test 4 hours 110. 8 hours. 6 hours 111. 8 27 hours. Control oil 107. Below 1 hour.

Example IX 100 g. refined, bleached cottonseed oil were mixed with 20% by Weight of dimethylformamide in an Erlenmeyer flask. The same test conditions were used as in Example VIII. Results:

Chilling time I.V. Cold test 3% hours 109. 3 8 hours. 5 hours 111. 8 28 hours. Control 011 107. 5 Below 1 hour.

From the foregoing description and examples it will be seen that a process has been provided for Winterizing oils which, with low quantities of solvent, moderate temperatures, and relatively short holding periods, results in a product oil in high yield and high quality, exceeding the necessary cold test requirements for salad oils as determined by A.O.C.S. methods. The process is well suited for continuous operation, requiring, in general, less than about six hours time from start to finish. Under the preferred conditions, the normal overall operating time lies between about three and four and one-half hours. A choice of solvents depending upon their availability and cost is possible, and the solvents and/or oil may be used in either anhydrous form or while mixed with water. Rapid chilling in conventional chilling units is permissible, and no seeding operation to initiate crystallization is necessary.

We claim:

1. A process for the winterization of cottonseed oil comprising, mixing said oil with less than about by weight of an organic solvent selected from the class consisting of the low-molecular weight ketones, acetates, and ethers, rapidly chilling the resultant solution to a temperature within the range of from about 28 F. to about 39 F., maintaining the temperature of said chilled material within said range for a period of time not in excess of about eight hours to crystallize the highermelting triglycerides, separating the crystallized fraction from the liquid fraction.

2. The process of claim 1 wherein said solvent is acetone.

3. The process of claim 1 wherein said solvent is methyl ethyl ketone.

4. The process of claim 1 wherein said solvent is ethyl acetate.

5. The process of claim 1 wherein said solvent is isopropyl acetate.

6. The process of claim 1 in which said solvent is one with which water is soluble only to a limited degree and wherein said solvent is substantially saturated with water.

7. A process for the winterizaton of cottonseed oil comprising, mixing said oil with about 1 0% by weight of an organic solvent selected from the class consisting of the low molecular-weight ketones, acetates and ethers, rapidly chilling the resultant solution to a temperature in the range of from about 31 F. to 34 F., maintaining said temperature for a period of from about two to about six hours to provide a crystalline fraction, separating said crystalline fraction from the liquid fraction, and removing the solvent from said liquid fraction to provide a winterized salad oil.

8. The process of claim 7 wherein the chilled material is gently agitated during said crystallization period.

9. A process for the winterization of cottonseed oil comprising, mixing said oil with about 10% by weight of acetone, chilling the resultant solution to a temperature of about 32 F, maintaining said temperature for a period of at least about two hours but not greater than about six hours to provide a crystalline fraction, separating said crystalline fraction from the liquid fraction, and separating the acetone from said liquid fraction to provide a winterized salad oil.

10. A continuous process for the winterization of cottonseed oil comprising, continuously cooling a stream of said oil to a temperature within the range of from about 40 F. to about 60 PI; continuously introducing into said precooled stream of oil a stream of organic solvent of the class consisting of the low molecular-weight ketones, acetates, and others so as to provide less than about 15% by weight of solvent in the resulting oil-solvent solution; passing said solution through a rapid chilling unit to provide a. temperature within the range of from about 28 F. to about 34 F. in the efiiuent stream; continuously passing said chilled stream at said temperature through a holding unit while subjecting it to gentle agitation to thereby provide a crystalline fraction, the rate of passage through said holding unit providing a hold-up time of at least two hours but not greater than about six hours; continuously separating the efiluent from said holding unit to provide a solid fraction and a liquid fraction; separating the solvent from said liquid fraction to provide a winterized oil; and recycling said solvent for admixture with a further portion of said oil.

References Cited in the file of this: patent UNITED STATES PATENTS 2,450,235 Gee Sept. 28, 1948 2,619,421 Greenfield Nov. 25, 1952 2,684,378 Skau July 20, 1954 OTHER REFERENCES 7 Skau et al.: Journal Am. Oil Chemists Soc., vol. 27, No. 12, pp. 555-564, December 1950.

Boucher et al.: Journal Am. Oil Ch. Soc, vol. 29, No. 9, pp. 382-385, September 1952.

Boucher et al.: Journal Am. Oil Ch. Soc, vol. 29, No. 11, pp. 455-456, November 1952.

Boucher et al.: Journal Am. Oil Ch. Secs, vol. 31, No. 6, pp. 268-270, June 1954.

UNITED STATES PATENT OFFICE 0F cormsc'non Patenfo No. 2,910,363 October 27, 1959 Leon J. Rubin et a1.

- It, is hereby certified that error appears in the above numbered patent requiring correction and that -t he said Letters Patent should read as 'corrected below'.

In the drawing, for *"HIGH MELTING TRICLYCERIDES" read HIGH MELTING TRIGLYCERIDES in the printed specification column 1 line 56 for ;3method and" ra'ad method an column 5, line 44,' for !'water-solubili'ty" read solubility column 10, line 2, after "fraction" and before the period insert and removing the solvent from said latter fraction Signed and sealed this 14th day 61: Jun e 1960.

(SE L) Atiast:

KARL H. AXLTINE aon'rza'r c. WATSON Attes'bing Offier Comiaaiomr cf Patents 

1. A PROCESS FOR THE WINTERIZATION OF COTTONSEED OIL COMPRISING, MIXING SAID OIL WITH LESS THAN ABOUT 15% BY WEIGHT OF AN ORGANIC SOLVENT SELECTED FROM THE CLASS CONSISTING OF THE LOW-MOLECULAR WEIGHT KETONES, ACETATES, AND ETHERS, RAPIDLY CHILLING THE RESULTANT SOLUTION TO A TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 28* F. TO ABOUT 39* F., MAINTAINING THE TEMPERATURE OF SAID CHILLED MATERIAL WITHIN SAID RANGE FOR A PERIOD OF TIME NOT IN EXCESS OF ABOUT EIGHT HOURS TO CRYSTALLIZE THE HIGHERMELTING TRIGLYCERIDES, SEPARATING THE CRYSTALLIZED FRACTION FROM THE LIQUID FRACTON. 